Vessel for treatment of fragmentary material



Dec. 27, 1960 c. L. DURKEE 2,966,215

VESSEL FOR TREATMENT OF FRAGMENTARY MATERIAL Filed May 1, 1957 5 Sheets-Sheet 1 INVENTOR 'CAWK QMM 62d", z W

ab 4 M ATTORNEYS Dec. 27, 1960 c. DURKEE VESSEL FOR TREATMENT OF FRAGMENTARY MATERIAL Filed May 1, 1957 5 Sheets-Sheet 2 INVENTOR can 1. EM,

BY 4 w, M

AT TORNEY5 Dec. 27, 1960 c. L. DURKEE 2,956,215

Q VESSEL FOR TREATMENT OF FRAGMENTARY MATERIAL Filed May 1, 1957 5 Sheets-Sheet 4 4/ INVENTOR MJ AYLEM, MMTM ATTORNEYJ Dec. 27, 1960 c.1 DURKEE 2,966,215

VESSEL FOR TREATMENT OF FRAGMENTARY MATERIAL Filed May 1, 1957 5 Sheets-Sheet 5 la 5 INVENTOR H] CZaM ffbmiul BY 0w, 47% w,

ZlZL q/ L ATTORN EY5 VESSEL FOR TREATMENT OF FRAGMENTARY MATERIAL Clarence L. Durkee, 627 Jackson St., Wausan, Wis.

Filed May 1, 1957, Ser. No. 656,324

Claims. (Cl. 162-237) This invention relates to apparatus for treating fragmentary material by introduction to a cooking vessel and subjection to the treating action of a fluid, wherein the vessel of the apparatus is divided into a pair of closely adjacent conveyor flight passages with conveyor flights on a continuous belting traveling through the passages, said conveyor flights covering a substantial portion of the cross-section area of the passages to move the material through the vessel with little mechanical turbulence, and at the turn leading from one passage to the other there is provided, in a preferred form of the invention, an end wall having a surface that conforms to the arc swept by the flight edges as they turn in their travel from one passage to the other, which end wall is adjustable in position for maintaining the surface thereof in close proximity to the flight edges.

The invention is particularly directed to an apparatus adapted for the treatment of fragmentary material by exposure to a treating liquor or vapor, or both, wherein a thorough contacting of the material is to be had by such liquor or vapor. The treatment is carried out with a minimum of disturbance and agitation, to prevent undesirable mechanical breakdown of the fragments of material. Such manner of treatment is particularly desirable in the reduction of wood chips for pulp, in the manufacture of paper. The chips are exposed to chemical agents that attack and digest the lignin holding the fibers together. This process of freeing the fibers should be carried out with a minimum of actual disintegration, either by result of mechanical reduction or chemical over-treatment of portions of a batch.

In the practice of the invention a vessel is divided to provide a pair of closely adjacent passages for conveyor flights. The conveyor flights are on a continuous belt moving through both passages, such that flights in one passage travel in a direction opposite to those in the other passage. As the flights pass from one passage to the other they reverse their direction of movement and sweep through an arcuate path. To maintain a uniform movement of the fragmentary material with the flights, a curved wall section is placed about the arcuate path swept by the flights in close adjacency to the outer edges of the flights. In this manner the material is properly retained between the flights, and at the rate of movement at which the apparatus is operated uneven distribution of material, compacting and non-uniform advancement of the material is eliminated. The curved wall section is telescoped within the vessel, which defines the outer walls of the passages, and is movable therein. Preferably, this wall section supports a tail end guide for the belting of the flights and is urged rearwardly. The belting is then kept relatively taut and the curved wall section is retained at a fixed position with respect to the arcuate path of the flights as wear in the belting works an increase in belt length.

In one particular form of the invention material to be treated is introduced to flights traveling in one direc- States Patent 0 tion, and is subsequently transferred to flights traveling in the opposite direction in advance of the reversal of flight direction. That portion of flight movement in which an arcuate path is traveled to reverse the direction of flight travel is thereby bypassed by a large portion of the treated material. This mode of operation is adaptable to granular materials, of which the individual fragments move quite freely of one another and will readily descend from one passage to another without adverse conglomeration.

The invention as described and set forth in the illustrations herein will find its primary use in the digestion of wood, and other fibrous material, into pulp suitable for paper making. In describing the invention particular reference will be made to this manner of use, and it is to be understood that the scope of the invention is not to be restricted to such use by reason of specific reference thereto. The invention may find widespread use in the treatment of other materials of fragmentary or shredded nature.

It is an object of the invention to provide an apparatus for the continuous digestion of a material wherein the apparatus is wholly contained within a vessel of compact cross-section dimension having inherent strength to withstand internal pressures conducive to the digestive process.

It is another object of this invention to provide an apparatus for the continuous digestion of a material wherein such material may be placed in and removed from the apparatus on a common floor level.

It is another object of the invention to provide conveyor flights for moving material through a digestion apparatus wherein the material may be bypassed from that part of the run of the flights in which direction of travel is reversed.

It is another object of this invention to provide conveyor flights for moving material through a digestion apparatus that are carried by a chain drive in which slack developed therein is taken up without affecting the spacing between the flights and passage walls through which they pass.

It is another object of this invention to provide an apparatus for the treatment of fragmentary material having conveyor flights for moving the material in which the flights are mounted to have a minimum imbalance of loading.

The foregoing and other objects and advantages of this invention will appear from the description to follow. In the description reference is made to the accompanying drawings, which form a part hereof, and in which there is shown by way of illustration and not of limitation a specific form in which this invention may be embodied.

In the drawings:

Fig. 1 is a side view in elevation of a continuous digester embodying the invention,

Fig. 2 is a side view of the continuous digester taken in section along the longitudinal center line of the apparatus,

Fig. 3 is a fragmentary side view in elevation taken on the same plane as that for Fig. 2 showing roller chain and driving means therefor at the head end of the digester,

Fig. 4 is a fragmentary view in section of the portion of the apparatus shown in Fig. 3 taken on the plane 4-4,

Fig. 5 is a view in cross-section of the digester taken on the plane 5-5 indicated in Fig. 2,

Fig. 6 is a fragmentary view in section of the tail end of the digester taken through a vertical plane passing through the longitudinal center line of the apparatus, and with chain and conveyor flights broken away and removed,

Fig. 7 is a view in cross-section of the tail end of the digester taken on the plane 7--7 indicated in Fig. 6,

Fig. 8 is a fragmentary view in section of the tail end of the digestertaken on the plane 8-8 indicated in Fig. 6, and

Fig. 9 is a fragmentary view of the roller chain and a flight attached thereto.

Referring now to the drawings, and more particularly Fig. 1, there is shown an inclined cooking vessel 1 comprised of a cylindrical shell 2, a head cap 3 and a tail cap 4. An intake 5 of generally inverted frusto-conical configuration is mounted on the upper side of the shell 2, and upon the intake 5 there is placed a rotary valve 6 which is fed from a hopper 7. Fragmentary material, such as the wood chips 63 shown in Fig. 1 that is to be treated in the vessel 1 is placed in the hopper 7, and if 'desiredthe interior of the hopper 7 may be heated to drive ofi gaseous products in the material as a pre-conditioning 'before introduction through the valve 6 to the interior of the vessel 1.

A spoked impeller wheel 8 of the valve 6 meters the 'fragmentary material 63 entering the vessel 1 to initiate a steady flow of uniform amount into and through the apparatus. The impeller wheel 8 also forms a pressure barrier permitting maintenance of elevated pressures within the vessel 1, that are essential to many of the be adopted, such as a plunger feeder, a set of escape hatch valves, or a screw feed that forms a plug of material through compaction thereof. If elevated pressures are not to be maintained in the vessel 1 a pressure bar- 'rier inlet device may be dispensed with.

A funnel like exit duct 10 extends downwardly from the underside of the upper end of the cylindrical shell 2 and leads to a material discharging apparatus 11, which in turn feeds a conveying duct 12. The discharging apparatus 11, as shown, comprises a screw feed impeller, the construction of which is known. A screw feed compacts the treated material, as it is moved along through the impeller, to form a pressure resistant plug, and in this manner pressures are retained within the vessel 1. The apparatus 11 may take one of several forms, a rotary valve, such as the valve 6, may be employed, or a plunger feeder, an orifice discharge, or a set of escape hatch valves may be employed. Also, in the instance of pulping the fragmentary material may be led through the duct 10 directly to an attrition mill that incorporates the necessary pressure barrier.

The cylindrical shell 2 is supported at its head end by the intake 5 and duct 10. The shell 2 is further supported at the bottom by resting a pad 13 upon a fixed abutment 14. The pad 13 is free to slide upon the abutment 14, to allow for expansion and contraction in response to periodic heating and cooling. A steam pipe 15 feeds a horizontal steam input manifold 16 that encircles the cylindrical shell 2 at a level beneath the junctions of the intake 5 and exit duct 10 with the shell 2. This level 1s nearly coincident with the intended liquor level within the vessel 1. For different treating processes the manifold 16 may be located at other levels to satisfy heating requirements. Extendingdownwardly from the manifold 16 is a plurality of steam tubes 17 that terminate at their lower ends in a juncture with a ring shaped condensate manifold 18 encircling the shell 2. Each of the steam tubes 17 is welded to the outer surface of the shell 2, and with a passage of steam through the tubes 17 heat is transferred to the interior of the vessel 1 to elevate temperatures to desired cooking level.

Referring now to Fig. 2, there is shown a partition 19 that divides the interior of the cylindrical shell 2 longitudinally. into an upper flight passage 20 and a lower flight passage 21. As is shown in Fig. 5, the partition 19 extends across the entire width of the shell 2, so that the lower side.

upper flight passage 20 and lower flight passage 21 are fully separated from one another throughout the length of the partition 19. The lower terminus 22 of the partition 19 is at a substantial distance above the lower end of the shell 2, as is clearly indicated in Figs. 2, 6 and 8. The upper end of the partition19 terminates at a relatively short distance below the upper end of the shell 2 with a tab 23 centrally located from the sides of the shell 2, as shown in Figs. 2, 3 and 4. Attached to the tab 23 is a sleeve 24 surrounding a shaft bearing 25. The shaft bearing 25 receives a drive shaft 26 and supports the shaft 26 at a point medial the 'two sides of the shell 2. The drive shaft 26 is also borne by two bearings 27 that include appropriate packing glands to retain pressure differentials between the interior and exterior of the vessel 1. Each bearing 27 is capped by a plate 28, through which the shaft 26 extends, and the ,righthand end of the shaft 26, as viewed in Fig. 4, carriesa drive sprocket 29 driven by a chain 30. The chain 30, in turn, is driven by means not shown.

Adjacent each end of the shaft bearing 25 is a keyed hub 31 of a six tooth sprocket wheel 32. A continuous roller chain 33 engages each sprocket wheel 32, to be driven thereby upon rotation of the shaft 26 in response to the driving chain 30. Each chain 33 encircles the partition 19 and as it leaves its sprocket wheel 32 moves downwardly through the upper flight passage 20. The action of the sprocket whees 32 draws the chains 33 upwardly through the lower flight passage 21. To guide the continuous roller chains 33 there is provided a set of four rail plates 34 fixed in upstanding positions upon the par tition 19. Two of the rail plates 34 are on the upper side of the partition 19 and two of the plates 34 are on the Bach rail plate 34 is in alignment with a sprocket wheel 32 and the outstanding edges of theplates 34 thus provide rails upon which the roller chains 33 will ride as they traverse about the partition 19.

To provide a track at the tail end of the vessel 1, about which each roller chain 33 may turn to reverse its direction of travel, there is provided a pair of end rails 35. Each rail 35 is aligned with a pair of rail plates 34 and serves as a means for establishing a definite track for a chain 33. The configuration of a rail 35 is clearly shown in Fig. 6, and as shown therein presents a circular curve about which a chain 33 may reverse its direction of travel.

Each end rail 35 is supported on a transverse strut 36 extending between the sides of the shell 2 and laying in a common plane with the partition 19. The outer ends of the strut 36 are secured, by welding, to a false bottom 37 comprised of a spherical end 38 that joins with a short cylindrical sleeve portion 39 telescoped within the cylindrical shell 2 with a close fit. In the particular form of the invention shown the strut 36 is spaced a substantial distance below the lower terminus 22 of the partition 19 to form a gap 49 therebetween. The purpose of the gap is discussed hereinafter. If it is desired to dispense with gap 49 the partition 19 may be extended downward, or the strut 36 upwardly, to effect a meeting of these parts in which one overlays the other in a shingle efiect, whereby relative axial movement may occur.

A pair of slits 40 are cut in the sleeve portion 39 of the false bottom 37 at diametrically opposite sidesto engage fixed runners 41 on the inside of the shell 2. In this fashion the false bottom 37 is prohibited from twisting, so that the end rails 35 are held in alignment with the four rail plates 34, while permitting axialmovement of the false bottom 37 for tensioning the chains 33 and varying the distance of the run for the'chains 33 as wear occurs, or links are removed. 7 V V 7 As shown in Fig. 8, a pair of adjustment rods '42 are welded to the outer convex surface of the false bottom 37. Each rod 42 extends through a short length of piping 43, which provides an exit from the tail cap 3. Each rod 42 also passes through a packing gland 44 and presents a threaded end 45 to the exterior of the vessel 1. An adjustment nut 46 is threaded upon each rod 42 and a pair of springs 47 that encircle the rods 42 are inserted between the nuts 46 and packing glands 44. The springs 47 urge the false bottom 37 and its associated end rails 35 downwardly and thereby tension the chains 33 and take up slack in the chains 33 as it develops through normal wear.

A plurality of generally semi-circular conveyor flights 48 formed from sheet material are welded at evenly spaced intervals to links of the roller chains 33. Each flight 48 is perforate and has a peripheral configuration that closely matches the outline of the flight passages 29 and 21, as shown in Fig. 5. The points of attachment of each flight 48 to the chain links fall on a line passing through or close to the center of gravity of the flight 48. By virtue of this manner of mounting the flights 48 there is a minimum of turning moment acting to depress or elevate the chains 33.

Each flight 48 has a pair of recesses 53 that match the hubs 31 of the sprocket wheels 32, which recesses 50 are partially formed by cars 51 that are closely spaced from the sides of the rail plates 34. The ears 51 function as guides to block excessive sidewise movement of the flights 48 by striking the rails 34. Movement of the flights 48 lateral to the direction of chain travel is also limited by provision of a plurality of wear plates 52 placed along the lower inside of the shell 2, and a similar set of wear plates 53 placed along the upper inside of the shell 2. The plates 52, 53 relieve the sides of the shell 2 from wear, which may otherwise occur by reason of slack in the chains 33, or the presence of forces acting to raise the flights 48 within the passage 29.

An inlet pipe 54 for a treating liquor is provided, as shown in Figs. 1 and 2, at a point below the intake 5 at a height slightly above the intended liquor level. An additional pipe 55 is shown near the top of the shell 2, through which vapor may pass for maintaining desired pressure or other conditions. The pipe 55 also may serve as a means for flushing the interior of the vessel 1 for cleaning purposes, or at times may be employed when a wash is desired. The exact placement and nature of inlet pipes may vary in accordance with the precise nature or" the process to be carried out.

T o extract spent liquor from the vessel 1 there is provided an outlet box 56, that is shown in Figs. 1 and 2. The outlet box 56 comprises an outstanding wall on the underside of the vessel 1 coincident with the liquor level, and a screen 57 separates the interior of the box 56 from the interior of the vessel 1. The fragmentary material is thus precluded from departing through the box 56 and the outlet pipe 58 leading therefrom. As in the instance of the inlets for the vessel 1, the position of the outlet box 56 may vary from installation to installation, as well as the number of outlets employed.

The chamber 59 that is formed between the tail cap 3 and the false bottom 37 is provided with a drain 6% and an inlet 51, to provide a means for cleansing and washing down this chamber. The inlet 61 is joined through a pipe 62 to the principal interior of the vessel 1, thereby minimizing any pressure differential between the chamber 59 and the principal interior. The build up of damaging pressures upon the spherical end 33 of the bottom 37 is hence eliminated. The outlet 6% is periodically opened to flush the chamber 59 and keep the same clear of particle sediment, for insuring freedom of movement of the false bottom 37.

The place of introduction of material to the vessel 1, through the intake 5, is on the leaving side of the chains 33, with respect to the driving sprockets 32. At this position the material is carried by the flights 48 slowly downward to the treating liquor. In typical pulping applications the rate of travel may be no more than a foot per minute and where attack by vapor is advantageous to remove gases a steaming stage is had. Upon submerout resort to mechanical agitation.

sion in the liquor little additional gaseous evolution will occur and the gas that is evolved may readily travel along the inclined side of the shell 2.

For pulping, the liquor may be that for the sulfite or sulphate process, or the soda process, all of which are well known for chemically pulping cellulosic materials. The liquid level in the vessel 1 will be at, or near, the height of the outlet box 56, and the steam input manifold 16 is disposed coincident with this level, to impart heat directly to the treating liquor. Heating and pressure within the vessel 1 causes a thorough intermixing of the liquor and the fragmentary material with- Uniform treatment, and hence a uniform product, is achieved.

The downward movement of the flights 48 in the passage 29 carries the material positively along through the vessel 1 at a uniform rate of travel. As the flights 48 descend through the upper passage 20 and pass the lower terminus of the partition 19 the material will descend through the gap 4? to the ascending flights 48 moving upwardly into the passage 21. The bulk of the material thus by-passes the travel of the flights 48 about the end rails 35, and the flights are thus substantially free of material as they make the turn about the end rails 35 to reverse the direction of travel. The presentation of the gap 49 is particularly advantageous for granular materials that will readily descend by their own accord. Stringy materials, on the other hand, are usually carried around the turn by the flights, and the gap '49 may be dispensed with. In some instances auxiliary means may be utilized for discharging material from the descending flights 48 to the ascending flights 48 through the gap 49. A mechanical pusher, or a wholly contained fluid pump may be disposed at the gap 49 to cause a positive displacement of the material from one set of flights to the other.

As the material ascends with the flights 48 in the passage 21 it approaches the exit duct 1t}, located above the liquid level of the treating liquor. As the material leaves the liquor it drains, and the incline of the flights 43 facilitates drainage to the lower side of the shell 2, which in turn is inclined for effective drainage to the body of liquor. The angular tilt of the flights 43 also facilitates discharge of the material without need of accessory equipment for moving the material off the flights Gravity feed is utilized for both feeding in and discharging material trom the apparatus. the vessel 1 is a material aid in accomplishing such gravity feed. The discharge is complete before the flights 48 arrive at the sprocket wheels 32. The driving means for the continuous roller chains 33 is thereby kept free of fragmentary material, so that its action will not be impaired by any accumulation of the material, or by corrosive action of the liquor that might occur if saturated material were to be deposited thereon.

By attaching each flight 4 5 to a pair of chains 33 the flights 48 are firmly held from twisting and turning to- Ward tl e vessel sides. Also, by having the points of attachment of each flight to the chains 33 falling in a transverse line that is common with the center of gravity of the flight, the resistance of the liquor and fragmentary material to the flight will present a loading to the chains 33 in which turning moments above and below the chains are substantially canceled. To assist this cancellation of torques each flight 48 is of a uniform trbkness and presents substantially equal surface areas above and below the chains 33.

The surface of the spherical end 33 of the false bottom 37 is spaced from the end rails 35 at a distance such that the outer periphery of the flights 4% will closely pass. The fragmentary material being treated is then carried about the turn in a confined passage precluding a drift of the material from between the flights 453, Which would allow portions of the material to drop behind the pace of the flights 48 and accumulate. As slack develops The incline of in the chains 33, it is compensated for by movement of the rails 35. The false bottom 37 moves in unison with the rails 35 and hence the spacing between the flights 48 and spherical end 38 is properly maintained.

As is seen in Figs. 2 and 3 the partition 19 has an offset 63, near the upper end, that raises the partition above the center line of the shell 2. The flights 48 must be dimensioned to pass about the shaft 26, and as a result the lower edge of a flight 48 in the upper passage 20 is Well above the upper edge of a flight 48 in the lower passage 21. By offsetting the partition 19 above the center line the spacing between the lower edges of all flights and the passage walls directly beneath may be at a minimum. Seepage of fragmentary material about the flight edges is inhibited, and the advantage of having a continuous digester in a single cylindrical vessel is maintained.

extending flight passages, the division between the flight passages terminating at a spaced distance from the tail end of the vessel; conveying means within said vessel encircling the division between and extending through each of the flight passages; conveying flights spaced along said conveying means; driving means for engaging and moving the conveying means through the flight passages; a guide at the tail end of the vessel about which said conveying means is moved to reverse its direction of movement from one flight passage to the other, said guide being movably mounted for longitudinal movement with respect to said vessel; a false bottom within the tail end spaced from said guide which is movable with the guide to retain a set spacing therebetween and which has an inner surface that substantially conforms to the envelope swept by the outer edge of a flight as such flight moves about said guide; and means to move the guide and false bottom toward the tail end to reduce slack in the conveying means.

2. In an apparatus for the treatment of cellulosic fragmentary material by exposure to a digesting fluid under heat and pressure the combination comprising: an elongated vessel having a head end and a tail end divided over a major portion of its length into a pair of longitudinally extending flight passages, the division between the fiight passages terminating at a distance from both the head end and the tail end of the vessel; a conveying means within said vessel encircling the division between and extending through each of the flight passages; conveying flights spaced along said conveying means; driving means for engaging and moving the conveying means through the flight passages; a guide at the tail end of the vessel about which said conveying means is moved to reverse its direction of movement from one flight passage to the other, said guide being spaced from the end of the division between flight passages whereby material being conveyed can pass from conveying flights leaving one passage to conveying flights entering the other passage without passing about said guide at the tail end; a movable mounting for said guide at the tail end that includes a curved bottom wall within the vessel that is spaced from the extremity of the tail end whereby the guide and curved bottom wall move together to retain a fixed spacing therebetween and which has an inner surface that substantially conforms to the envelope swept by the outer edge of a flight as such flight moves about said guide; means to move the guide at the tail end and its mounting to reduce slack in the conveying means; an entrance to said vessel entering upon the flight passage in which the conveying means is on the leaving side of the driving means; and a discharge opening for said vessel extending from the flight passage in which the conveying means is on the approaching side of the driving means.

-3. In an apparatus for the treatment of cellulosic fragmentary material by exposure to a digesting fluid under heat and pressure the combination comprising an elongated vessel set on an incline; a longitudinal partition within said vessel dividing the same into an upper and a lower passage, which partition terminates short of the ends of the vessel; conveying means encircling the partition; conveying flights attached to said conveying means disposed at a substantial angle from the horizontal; driving means for moving the conveying means downwardly through the upper passage and upwardly through the lower passage; a conveying means guide within the lower end of the vessel; a false bottom telescoped within the vessel which supports said guide and which has an inner surface that substantially conforms to the envelope swept by the outer edge of a flight as such flight moves about said guide; means extending from the false bottom through the vessel to the exterior; and resilient means working on said means urging the means and the false bottom downwardly whereby said false bottom and guide will move in unison in response to the resilient means.

4. An apparatus as recited in claim 3 having an intake opening entering upon the upper passage and an exit duct leading from the lower passage.

5. An apparatus as recited in claim 3 having a connecting pressure equalizing pipe joining the lower side of the false bottom to the remainder of the interior of the vessel, and having an outlet for the vessel. on the lower side of the false bottom whereby the space on said lower side may be flushed.

References Cited in the file of this patent UNITED STATES PATENTS 203,887 Caldwell et al May 21, 1878 1,160,523 Morrow Nov. 16, 1915 1,297,569 Johnson Mar. 18, 1919 1,353,336 Getz Sept. 21, 1920 1,954,508 Winter Apr. 10, 1934 2,080,946 Lesher May 18, 1937 2,235,992 Hapman Mar. 25, 1941 2,335,611 Pray Nov. 30, 1943 2,425,335 Messing et a1 Aug. 12, 1947 2,488,671 Lehman Nov. 22, 1949 

